A Facile Microwave-Assisted Synthesis of Carbon Dots and Their Application as Sensitizers in Nanocrystalline TiO₂ Solar Cells

Carbon quantum dots (CQDs or CDs) recently have attracted attention due to their unique optical and chemical properties. Herein we demonstrate a facile protocol to synthesize CDs via the microwave-assisted method. In this research, we use citric acid as carbon source and urea as nitrogen source. The UV-vis absorption of CDs show two peaks at 326 and 408 nm respectively correspond to the π→π∗ transition of C=C bonds and n→π∗ transition of C=O or other bonds on the CDs surface. The CDs solution emit green color emission at wavelength 521 nm λ _excitation = 365 nm), which the highest PL intensity is achieved by the CDs heated in microwave for 15 min. Moreover, we also conducted a preliminary study of the CDs as sensitizers in dye-sensitized solar cells (DSSCs) based on TiO₂ nanocrystalline. The power conversion efficiency (η), fill factor (FF) and short-circuit current density (J_sc) of 0.29%, 0.31 and 0.36 mA/cm², respectively, are achieved for the CDs based cell. This research suggests that the CDs have the potential application as sensitizers in DSSCs.